Corrosion preventing mount for electric water heaters



J. J. FINN Feb. 26, 1957 CORROSION PREVENTING MOUNT FOR ELECTRIC WATERHEATERS Filed June 17, 1955 United States Patent CORROSION PREVENTINGMOUNT FOR ELECTRIC WATER HEATERS John J. Finn, Allegan, Mich., assignorto Heatuhe Corporation, Allegan, Mich.

Application June 17, 1955, Serial No. 516,120

12 Claims. (Cl. 219-38) This invention relates to corrosion preventingmount for electric water heaters.

The principle objects of this invention are:

First, to provide a mounting for an immersion heating element in a Waterheater tank that will prevent or retard corrosion of both the tank andthe heating element sheath.

Second, to provide a mounting for the immersion heating element ofelectric water heaters which will prevent or retard corrosion of theheating element sheath and thus extend the effective life of the heatingelement.

Third, to provide an electrical discharge controlling clip for theimmersion heating element of an electric water heater to localize andcontrol the electrical dis charge of leakage current between the sheathof the heating element and the wall of the tank so that the heatingelement sheath is not attacked by electrolytic action.

Fourth, to provide simple and inexpensive means for lengthening theefiective life of the tank and immersion heating elements in electricwater heaters.

Fifth, to provide an electric water heater that prevents or controlsboth galvanic and leakage currents that tend to cause corrosion of thetank wall and heating element sheath.

Other objects and advantages of the invention will be apparent from aconsideration of the following description and claims. The drawings, ofwhich there is one sheet, illustrate a highly practical form of theelectrical discharge and corrosion control element of the invention.

Fig. 1 is a fragmentary perspective view of an immersion heating elementmounted in the wall of an electric water heater with the electricaldischarge and corrosion control elements operatively associated with theheating element.

Fig. 2 is a fragmentary horizontal cross sectional view through the tankand heating element taken along the plane of the line 2-2 in Fig. 3.

Fig. 3 is a fragmentary transverse cross sectional view through theheating element taken along the plane of the line 33 in Fig. 2.

Electric water heaters have conventionally been made of steel tankshaving zinc or other metallic coating on the inside to prevent rustingof the tank walls. Immersion electric heating elements have commonlybeen installed through a port in the tank wall and these heatingelements consist ofa copper or other metallic sheath enclosing anelectrical resistance heating element. The copper sheath for. theheating element is relatively inexpensive and forms a good heatconductor between the heating element and the water in which it isimmersed and at the same time is not subject to rusting due to thepresence of the water aroundthe sheath. However, it has been known forsome time that the dissimilar character of the metallic lining ofthetank and the metallic sheath of the heating element creates a galvanicaction similar to that of a battery withcurrent flowing through thewater in the tank between thetank wall and the sheath of the heatingelement; This electrolytic action results in corrosion or eating away ofthe material of the tank wall. This electrolytic action has been foundto be particularly objectionable when the copper sheath of the heatingelement is in direct electrical connection with the tank and its liningand to control the action it has been proposed to electrically insulatethe heating element sheath from the tank wall with electricallyinsulating gaskets. While the insulating gaskets for all practicalpurposes eliminate the battery type of corrosion they permit theestablishment of an electrical potential between the sheath of theheating element and the wall of the tank from which it is insulated anda new type of corrosion occurs at some indeterminate point on theheating element sheath where electrical discharge between the sheath andthe tank occurs. This new or different discharge is due to leakagecurrent from the resistance heating element in the heating elementsheath. When the heater is energized the resistance element is at highpotential relative to the tank which is grounded and due to theimperfect character of all insulating materials a small leakage currentfinds a path through the insulation in the sheath to the sheath and fromthere through the water to the tank wall. The current naturally followsthe shortest or easiest path to ground and will discharge off of apointed or curved surface in preference to a flat surface. In passingfrom the sheath the leakage current causes corrosion or erosion of theheating element sheath and ultimately the .sheath is punctured causingcomplete and rapid failure of the insulation around the resistanceelement.

The present invention greatly extends the effective life of immersionheating elements by providing a controlled path for the discharge ofleakage currents between the sheath of the heating element and the wallof the tank with the current passing through a clip or other piece ofmetal electrically connected to the heating element sheath so that theclip is eaten away in preferenceto the sheath.

In the drawings the tank wall of a water heater is indicated at 1 and itmay be assumed that the tank wall is coated on the inside with a zinc orother non-rusting metallic coating. The wall is pierced to form the port2 and provided with an external plate or ring 3 around the port thatforms an outwardly facing gasket seat. Seated against the ring 3 is agasket 4 of electrically insulating material. Seating against the gasketis a sealing plate 5 preferably formed of copper. The plate 5 is firmlyand sealingly clamped against the gasket by means of a backing plate 6held in place by bolts 7 as is common in water heater construction.Galvanic discharge between the heating element and the tank is preventedas has previously been disclosed by an insulating sheet 6A locatedbetween the plate 5 and the plate 6.

The copper sealing plate 5 is provided with two flanged apertures 8within the outline of the hole in the gasket 4 and these apertures passthe outwardly extending legs 9 of a U-shaped tubular sheath 10 desirablyformed of copper. The surface of the copper sheath 10 is fused orintegrally connected with the sealing plate to prevent leakage of wateralong the surface of the sheath. The backing plate 6 supports thesealing plate and resists the pressure of the water within the tank onthe sealing plate. As is common in electric water heaters, the arms ofthe sheath project through holes provided therefor in the backing plate.An insulating terminal block 11 surrounds the outer ends of the sheathand the electrical conductors 12 that project from the sheath. Theconductors 12 are electrically connected within the sheath to a coiledresistance element 13 that is electrically insulated within the sheath.

The electrical discharge and corrosion control element 14- consists of alooped strip of metal, preferably of Patented Feb. 26, 1957 grassescopper the same as the sheath 10, positioned between the arms 9 of thesheath and within the port 2. The clip 14 is a multi-sided loop havingconcave sides 15 yieldably engaged between the branches of the sheathand other concave sides 16 connecting the ends of the sides 15. Theseveral side reaches of the clip 14 are connected by a plurality offolds or bends 17, the outer edges of which form outwardly convex pointsor ridges opposed to the inner surface of the tank and port 2.

As is more readily apparent from'Fig. 3 the external points 17 on thecontrol clip are desirably extended beyond the circumference of the holein the gasket 4 so as to be positioned closer to the inner wall of theport 2 than the side surfaces of the branches 9. However, this closespacing is not absolutely essential as electrical discharge will takeplace between two ports at diiferent electric potential at points wherethe parts are pointed in preference to fiat or rounded surfaces. Sincethe clip 14 is positioned within the port 2 the external points orridges 17 are opposed to the edge of the tank around the port andelectrical discharge between the tank wall and the heating elementsheath due to leakage current will take place between points or ridgesof the clip and the edge or inside surface of the port 2. The points orridges of the clip 'will thus be eaten away before any harmful corrosionoccurs in the sheath 1G and it is pointed out that the corrosion actionon the clip 14 is progressive from one point or ridge 17 to another withthe closest spaced ridge 17 being eaten away first until another ridgepresents a shorter path between the tank surfaces and the clip. The clip14 thus effectively delays and substantially prevents corrosion of theheating element sheath and greatly extends the life of the heatingelement by preventing failure of the heating element due to corrosion ofthe sheath. An electric water heater provided with the heating elementmount as described is thus protected against corrosion due to galvanicaction and also leakage currents and the effective life of the heater issubstantially extended.

Having thus described the invention, what is claimed as new and isdesired to be secured by Letters Patent is:

,1. An electric water heater comprising a tank having a zinc coatingon'the inside thereof and a port formed in the wall thereof with agasket seat surrounding the outside of the port, a U-shaped sheath ofcopper tubing projecting through said port with its ends locatedexteriorly of the tank, a plate of corrosion resistant copper havingholes therein passing the ends of said sheath with the surface of'theplate integrally sealed around the surfaces of the sheath, anelectrically insulating gasket positioned between said plate and saidseat, a backing member clamping said plate and said gasket against saidseat and insulated from said plate, an electric heating element in saidsheath having its ends exposed on the outer side of said backing member,and a discharge localizing clip of copper mounted between the branchesof said sheath and within said port, said clip being a multi-sided loopwith concave sides yieldably engaging said sheath and having a pluralityof externally convex corners between said sides projecting into moreclosely spaced relation with the inner surface of said port than thespace between the exposed surfaces of said sheath and the inner surfacesof said port.

2. An electric water heater comprising a tank having a port formed inthe wall thereof with a gasket seat surrounding the outside of the port,a U-shaped sheath of corrosion resistant tubing projecting through saidport with its ends located exteriorly of the tank, a plate of corrosionresistant material having holes therein passing the ends of said sheathwith the surface of the plate integrally sealed around the surfaces ofthe sheath, an

electrically insulating gasket positioned between said plate and saidseat, a backing member clamping said plate and said gasket against saidseat and insulated from said plate, an electric heating element in saidsheath having its ends exposed on the outer side of said backing mem'her, and a discharge localizing clip of the same material as said sheathmounted between the branches of said sheath and within said port, saidclip being a multi-sided strip with concave sides yieldably engagingsaid sheath and having a plurality of externally convex corners betweensaid sides projecting into more closely spaced relation with the innersurface of said port than the space between the exposed surfaces of saidsheath and the inner surfaces of said port.

3. An electric water heater comprising a tank having a metallic surfaceon the inside thereof and a port formed in the wall thereof with agasket seat surrounding the outside of the port, a U-shaped sheath ofmetal tubing dissimilar to the metal of'said surface projecting throughsaid port with its enos located exteriorly of the tank, a plate ofcorrosion resistant metal having holes therein passing the ends of saidsheath with the surface of the plate integrally sealed around thesurfaces of the sheath, an electrically insulating gasket positionedbetween said plate and said seat, a backing member clamping said plateand said gasket against said seat and insulated from said plate, anelectric heating element in said sheath having its ends exposed on theouter side of said backing member, and an electrical dischargelocalizing clip of metal mounted between the branches of said sheath andwithin said port, said clip being a multi-sided loop of the samematerial as said sheath with concave sides yieldably engaging saidsheath and having a plurality of externally convex corners between saidsides projecting into more closely spaced relation with the innersurface of said port than the space between the exposed surfaces of saidsheath and the inner surfaces of said port.

4. An electric water heater comprising a tank having a metallic surfaceon the inside thereof and a port formed in the wall thereof with agasket seat surrounding theoutside of the port, a U-shaped sheath ofmetal tubing projecting through said port with its ends locatedexteriorly of the tank, a plate of corrosion resistant metal havingholes therein passing the ends of said sheath with the surface of theplate sealed around the surfaces of the sheath, said plate being sealedto said seat and electrically insulated from the tank, an electricheating element in said sheath having its ends exposed on the outer sideof said tank, and an electrical discharge localizing clip of metalmounted between the branches of said sheath and within said port, saidclip being a multi-sided loop with concave sides yieldably engaging saidsheath and having a plurality of externally convex corners between saidsides projecting into closely spaced relation with the inner surface ofsaid port.

5. An electric water heater comprising a tank having a port formed inthe wall thereof with a gasket seat surrounding the outside of the port,a sheath of corrosion resistant tubing projecting through said port withan end located exteriorly of the tank, a plate of corrosion resistantmaterial having a hole therein passing the end of said sheath with thesurface of the plate integrally sealed around the surfaces of thesheath, means electrically insulating said plate from said tank andsealing said plate to said seat, an electrical heating element in saidsheath having its ends exposed on the outer side of said tank, and anelectrical discharge localizing clip of the same material as said sheathmounted in electrical contact with said sheath and within said tank,said clip having a plurality of external convex points projecting intomore closely spaced relation with the inner surface of said tank thanthe space between the exposed surface of said sheath and the innersurfaces of said port.

6. An electric water heater comprising a tank having a port formed inthe wall thereof with a gasket seat surrounding the outside of the port,a sheath of corrosion resistant tubing projecting through said port withan end located exteriorly of the tank, a plate of corrosion resistavsaasa ant material having a hole therein passing the end of saidsheath with the surface of the plate sealed around the surfaces of thesheath, means electrically insulating said plate from said tank andsealing said plate to said seat, an electric heating element in saidsheath having its ends exposed on the outer side of said tank, and anelectrical discharge localizing clip of metal mounted in electricalcontact with said sheath and within said tank, said clip having aplurality of external convex points projecting into closely spacedrelation with the inner surface of said tank 7. An electric water heatercomprising a tank having a port formed in the wall thereof with a gasketseat surrounding the outside of the port, a sheath of corrosionresistant tubing projecting through said port with an end locatedexteriorly of the tank, means sealing said sheath to said tank andelectrically insulating the sheath from the tank, an electric heatingelement in said sheath having its ends exposed on the outer side of saidtank, and an electrical discharge localizing clip of metal mounted inelectrical contact with said sheath and within said tank, said cliphaving a plurality of external convex points projecting into closelyspaced relation with the inner surface of said tank.

8. An electric water heater comprising a tank with a port therein, asheath of corrosion resistant tubing projecting into said port with anend located exteriorly of the tank, means sealing said sheath to saidtank and insulating the sheath from the tank, an electric heatingelement in said sheath having its ends exposed on the outer side of saidtank, and an electrical discharge localizing clip of metal removablymounted in electrical contact on said sheath and within said tank, saidclip having a point projecting into closely spaced relation with theedge of said port.

9. An electric water heater comprising a tank having a port formed inthe wall thereof with a ring surrounding the outside of the port andforming a seat, a sheath of corrosion resistant tubing projecting intosaid tank with an end located exteriorly of the tank, means sealing saidsheath to said seat and insulating the sheath from the tank, an electricheating element in said sheath having its ends exposed on the outer sideof said tank, and an electrical discharge localizing member of metalmounted in mechanically supported electrical contact on said sheath andwithin said tank, said member having a point projecting into closelyspaced relation with the inner edge of said port.

10. In an electric water heater having a metallic walled container withan immersion heating element with a sheath of metal dissimilar to themetal of the container projecting into the container and electricallyinsulated therefrom, an electrical discharge control element consistingof a piece of metal supported in yieldable contact with said sheath andhaving a plurality of pointed projections extending into more closelyspaced relation with the wall of said container than the closest spacebetween the surfaces of the sheath and the container.

11. In an electric water heater having a metallic walled container witha port therein and an immersion heating element with a sheath of metalprojecting into the container in spaced branches and electricallyinsulated therefrom, an electrical discharge control element consistingof a piece of metal supported in yieldable slidable contact between thebranches of said sheath and extend ing into more closely spaced relationwith the edge of said port than the closest space between the surfacesof the sheath and the container.

12. In an electric water heater having a container with an immersionheating element with a sheath of metal pro jecting in two spacedbranches into the container and insulated from the container, anelectrical discharge control element consisting of a piece of foldedmetal having spaced arms yieldably supported in contact between thebranches of said sheath and having a pointed projection extending intoclosely spaced relation with the wall of said container.

References Cited in the file of this patent UNITED STATES PATENTS

